1. Field of the Invention
The present invention relates to an electronic camera and an image generating apparatus which are applied to pickup of stereo images, and more specifically, to an electronic camera and an image generating apparatus which generate a stereo image enabling an appropriate print photograph to be obtained even if a multi-lens stereo image is picked up or generated.
2. Description of the Related Art
Various systems have been proposed which photograph and record an image containing stereoscopic information and which reproduce the image for observation. Among these systems, what is called a binocular stereo system has long been utilized which records two images having a parallax corresponding to the viewpoints of the right and left eyes and which present these images for the respective eyes. This is because this configuration is simplest and inexpensive, and effective.
For what is called the personal use of the binocular stereo, a system using stereo pair images, which is most basic and traditional, is now widely used to enable very clear images to be very inexpensively observed; however, the system is limited in that it allows only one person to observe the image at a time.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2002-218506 discloses a stereo image pickup apparatus using a stereo adapter. In this apparatus, a system controller is provided with a stereo adapter detecting section that detects that a stereo adapter has been attached, an automatic exposure (AE) control section that analyzes an object image signal relating to a photometric area to calculate photometric information required for exposure control, and a photometric area setting section that sets the photometric area. The photometric area setting section has a function for setting different photometric areas for a normal photographing mode and for a stereo photographing mode. Consequently, the optimum photometric areas are set for the normal photographing mode and for the stereo photographing mode.
If the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-218506 is used to pick up a stereo image, the stereo image to be recorded is expected to undergo appropriate exposure. However, if this image is printed, problems described below may occur notably with prints in print service laboratories that are popular in the market.
If a recording medium on which images are recorded is brought to a general laboratory for printing, recorded images (frames) are generally printed after automatically undergoing various types of image processing suitable for the respective images. A representative example is the correction of exposure. Even with an image subjected to a slight overexposure or underexposure during photographing, an image processing system of a print machine analyzes the level of a signal for the image to correct a luminance level (reflectance or density) during printing. As a result, an image at the appropriate luminance level is obtained.
In the correction of exposure during printing of a normal image, an averaging process is often employed which weights a central part of the image when analyzing the image signal level. That is, compared to the exposure control for a camera, the print machine carries out a signal level analysis corresponding to center emphasis average photometry (which is used to emphasize a main object, while avoiding impairing the entire image). Then, a luminance level (print density) output on the basis of the result of the analysis is corrected to print an appropriate desired image.
When the stereo pair image is printed, a phenomenon described below may occur compared to normal images. The stereo pair image is composed of two monocular images arranged side by side and corresponding to the right and left viewpoints. Accordingly, a central part of an object is located at two lateral positions, and a boundary portion between the monocular images is located in a central part of the entire stereo image. Thus, when the correction of exposure for normal images is applied, the exposure may not be corrected as intended (miscorrection). Specifically, when a stereo adapter is attached in the apparatus, eclipse shading is likely to occur in the boundary portion. Consequently, the luminance level of the boundary portion is prone to be low regardless of the original luminance levels of both monocular images. As a result, it is misunderstood that the main object is dark. Therefore, the exposure correction may result in overexposure in which the luminance level of the original image is abnormally high.
If the target is not a conventional film image but a digital image, the problem with the exposure during printing may result from the structure of a stereo image itself compared to the eclipse shading that may occur when the stereo adapter is attached. The reason will be described below.
For a conventional common stereo pair image, it is difficult to identify the boundary between two lateral monocular images. That is, provided that a display screen is viewed, it is difficult to determine whether the image is two lateral monocular images constituting a stereo image or a normal image having two similar lateral patterns.
With regards only to this, if marked eclipse shading is caused by the stereo adapter, it may actually advantageously serve as a mark for determining that the image is a stereo image. Of course, the eclipse shading caused by the adapter essentially disturbs the image. In addition, the eclipse shading varies depending on the characteristics of the main image pickup optical system, for example, an aperture value. Accordingly, the eclipse shading is not always useful.
Thus, to ensure such capability of visual determinations, it is possible to utilize the fact that digital images can be very easily processed (image processing). Specifically, a right and left monocular images for one stereo image to be generated are arranged away from each other. The area between these images is filled with black (luminance level of 0). Then, the area serves as what is called a median strip for the two images. This enables the stereo image to be visually directly determined. Such an area may be provided so as to surround the images (for example, like glasses frames) rather than being provided between the two images. Of course, in this case, the area provides similar functions.
Thus, a recording format with the above median strip or image frame is suitably employed as one for stereo images. However, in this case, the black median strip is present at a position similar to the one where the eclipse shading may occur when the stereo adapter is installed. This may result in similar miscorrection of exposure.
In the above description, for ease of under-standing, the stereo system is of the binocular type corresponding to the right and left eyes and the print system is the print service laboratory, which is popular in the market. However, of course, the above problems may also occur if an image recorded using a general multi-lens stereo system with three or more lenses is printed using a print apparatus having a function for correcting exposure (automatic luminance level adjustment).